Synchronization Stability Analysis of Current-Limited GFM Converters Considering Internal Voltage Amplitude Dynamics

Synchronization stability assessment of grid-forming (GFM) converters is essential during and after large disturbances in the external grid, where the active power control (APC) loop is perceived as the key concern since it is employed to generate the voltage phase angle. However, the impacts of the internal voltage amplitude dynamics and current saturation, determined by the reactive power control (RPC) loop and current limiter, are often neglected. This paper considers dynamic interactions between internal voltage magnitude and phase angle to derives an improved power-angle curve of the circular current-limited GFM converter, which facilitates more accurate identification of the critical angle margin for evaluating the synchronization stability after phase jumps. Furthermore, the impact of the RPC coefficient is quantified to provide parameter design recommendations for enhancing the post-phase jump synchronization stability. The analytical results are validated by simulations and experimental tests.